Image sensor device

ABSTRACT

An image sensor device includes a semiconductor device, a plurality of photo sensitive regions, a dielectric layer, a grid structure, and a plurality of convex dielectric lenses. The photo sensitive regions are in the semiconductor substrate. The dielectric layer is over a backside surface of the semiconductor substrate. The grid structure is over a backside surface of the dielectric layer. The grid structure includes a plurality of grid lines. Each of the grid lines comprises a lower portion and an upper portion forming an interface with the lower portion. The convex dielectric lenses are alternately arranged with the grid lines over the backside surface of the dielectric layer. Apexes of the plurality of convex dielectric lenses are higher than an interface between the upper portion and the lower portion of each of the grid lines.

PRIORITY CLAIM AND CROSS-REFERENCE

The present application is a continuation application of U.S. patentapplication Ser. No. 17/078,948, filed Oct. 23, 2020, now U.S. Pat. No.11,522,001, issued Dec. 6, 2022, which is a continuation application ofU.S. patent application Ser. No. 16/525,372, filed Jul. 29, 2019, nowU.S. Pat. No. 10,818,716, issued Oct. 27, 2020, which is a continuationapplication of U.S. patent application Ser. No. 14/109,318, filed Dec.17, 2013, now U.S. Pat. No. 10,367,021, issued Jul. 30, 2019, all ofwhich are herein incorporated by reference in their entireties.

BACKGROUND

Image sensor devices are widely used in various imaging applications andproducts, such as smart phones, digital cameras, scanners, etc.Typically, an image sensor device uses micro-lenses to condense incidentlight into color filters when the incident light first enters the imagesensor device. However, various dielectric films used in the imagesensor device with CMOS technology increase the number of optical paths,and such films are transparent to visible light. Even if the imagesensor device includes a grid to block the optical paths from crossingsubpixels, the incident light may dissipate (e.g. penetrate into otherpixels under the grid), in which a crosstalk issue arises, resulting insignal-to-noise ratio (SNR) degradation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1 illustrates a schematic cross-sectional diagram of an imagesensor device in accordance with some embodiments of the presentdisclosure;

FIGS. 2A-2B illustrate schematic enlarged partial views of the imagesensor device in FIG. 1 in accordance with various embodiments;

FIGS. 3A-3H illustrate schematic cross-sectional diagrams ofintermediate stages in accordance with a method for fabricating an imagesensor device in some embodiments of the present disclosure; and

FIG. 4 illustrates a flow chart of a method for fabricating an imagesensor device in accordance with some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The making and using of the present embodiments are discussed in detailbelow. It should be appreciated, however, that the present disclosureprovides many applicable concepts that can be embodied in a wide varietyof specific contexts. The specific embodiments discussed are merelyillustrative of specific ways to make and use the disclosed subjectmatter, and do not limit the scope of the different embodiments.

Terms used herein are only used to describe the specific embodiments,which are not used to limit the claims appended herewith. For example,unless limited otherwise, the term “one” or “the” of the single form mayalso represent the plural form. The terms such as “first” and “second”are used for describing various devices, areas and layers, etc., thoughsuch terms are only used for distinguishing one device, one area or onelayer from another device, another area or another layer. Therefore, thefirst area can also be referred to as the second area without departingfrom the spirit of the claimed subject matter, and the others arededuced by analogy. Moreover, space orientation terms such as “under”,“on”, “up”, “down”, etc. are used to describe a relationship between adevice or a characteristic and another device or another characteristicin the drawing. It should be noted that the space orientation term cancover different orientations of the device besides the orientation ofthe device illustrated in the drawing. For example, if the device in thedrawing is turned over, the device located “under” or “below” the otherdevices or characteristics is reoriented to be located “on” or “above”the other devices or characteristics. Therefore, the space orientationterm “on” may include two orientations of “above” and “below”.

Embodiments of the present disclosure are directed to providing an imagesensor device for better photo sensing quality. In each pixel region ofthe image sensor device, a convex dielectric lens is formed between acolor filter and a substrate for condensing incident light into a photosensitive element, such that quantum efficiency is improved and acrosstalk issue is avoided for high signal-to-noise (SNR) ratio, therebyimproving the photo sensing quality.

Referring to FIG. 1 , FIG. 1 illustrates a schematic cross-sectionaldiagram of an image sensor device 100 in accordance with someembodiments of the present disclosure. In the present disclosure, theimage sensor device 100 is a backside illuminated (BSI) image sensordevice. The image sensor device 100 includes pixel regions 100R, 100Gand 100B for converting incident light into RGB image data. It is notedthat the sequence of the pixel regions 100R, 100G and 100B shown in FIG.1 is shown as an example for explanation, and embodiments of the presetdisclosure are not limited thereto.

In FIG. 1 , the image sensor device 100 includes a substrate 110, photosensitive elements 120R/120G/120B, pixel circuits 122R/122G/122B, afirst dielectric structure 130, convex dielectric lenses 140, a grid150, a second dielectric structure 160, color filters 170R/170G/170B andmicro-lenses 180. The substrate 110 is a semiconductor substrate, whichincludes, but not limited to, a semiconductor wafer, asilicon-on-insulator (SOI) substrate, an epitaxial substrate. In someembodiments, the substrate 110 further includes an elementarysemiconductor such as silicon, germanium and diamond. In anotherembodiments, the substrate 100 further includes a compoundsemiconductor, such as silicon carbide, gallium arsenic, galliumcarbide, gallium phosphide, indium arsenide and indium phosphide, or analloy semiconductor, such as silicon germanium, silicon germaniumcarbide, gallium arsenic phosphide and gallium indium phosphide.

The substrate 110 has a front side 110A and a back side 110B. The photosensitive elements 120R/120G/120B are formed on the front side 110A ofthe substrate 110. The photo sensitive elements 120R/120G/120B areconfigured to receive the incident light transmitted from the back side110B through the substrate 110, and then to convert the incident lightto RGB image data. In some embodiments, the photo sensitive element120R/120G/120B are photodiodes, pinned photodiodes, partially pinnedphotodiodes, photogates or photo transistors.

The pixel circuits 122R/122G/122B are formed on the front side 110A ofthe substrate 110 and adjacent the photo sensitive elements120R/120G/120B respectively for electrical interconnecting with thephoto sensitive elements 120R/120G/120B, so as to transfer electriccharges generated from the photo sensitive elements 120R/120G/120B. Forillustration, each of the pixel circuits 122R/122G/122B includes a resettransistor, a source follower transfer, a row select transistor and atransfer transistor.

The first dielectric structure 130 is formed on the back side 110B ofthe substrate 110. In FIG. 1 , the first dielectric structure 130includes a first dielectric layer 132 and a second dielectric layer 134.The first dielectric layer 132 is formed on the back side 110B of thesubstrate 110, and the second dielectric layer 134 is formed on thefirst dielectric layer 132. The first dielectric layer 132 and thesecond dielectric layer 134 may include a transparent material, such assilicon oxide, silicon nitride, combinations thereof, or the like. Insome embodiments, that the material forming the first dielectric layer132 is selected to have a refractive index greater than that of thesecond dielectric layer 134.

In each of the pixel regions 100R/100G/100B, the convex dielectric lens140 is formed in the first dielectric structure 130. As shown in FIG. 1, the second dielectric layer 134 includes recesses for forming theconvex dielectric lenses 140 therein. At least one portion of each ofthe convex dielectric lenses 140 is located in the second dielectriclayer 134. In other words, a height of each of the convex dielectriclenses 140 may be greater than, equal to or smaller than a depth of eachof the recesses. Each of the convex dielectric lenses 140 has arefractive index lower than that of the second dielectric layer 134.Each of the convex dielectric lenses 140 has a convex side 140A and aplanar side 140B. The convex side 140A is oriented toward the incidentlight, whereas the planar side 140B is directly on the recess 136 andoriented toward the photo sensitive element 120R/120G/120B.

In some embodiments, the first dielectric structure 130 is a singlelayer structure. The first dielectric structure 130 may include atransparent material, such as silicon oxide, silicon nitride,combinations thereof, or the like. The first dielectric structure 130has a refractive index greater than that of each of the convexdielectric lenses 140.

The grid 150 is formed on the first dielectric structure 130. The grid150 separates the pixel regions 100R/100G/100B for preventing theincident light from passing therethrough. In some embodiments, the grid150 includes an insulating material such as silicon oxide, siliconnitride, silicon oxynitride, combinations thereof, or the like. In someembodiments, the grid 150 includes a metal material such as aluminum,copper, or the like, a metal alloy material such as aluminum alloy,copper alloy, or the like, a metal nitride such as titanium nitride,tantalum nitride, or other suitable material.

The second dielectric structure 160 is formed on the first dielectricstructure 130, the convex dielectric lenses 140 and the grid 150. Thesecond dielectric layer 160 may include a transparent material, such assilicon oxide, silicon nitride, combinations thereof, or the like. Thematerial of the second dielectric structure 160 is selected to have arefractive index smaller than that of each of the convex dielectriclenses 140. In some embodiments, the second dielectric structure 160 atleast partially covers the convex dielectric lenses 140.

The color filters 170R/170G/170B are formed on the second dielectricstructure 160 and respectively in the pixel regions 100R/100G/100B. Thecolor filters 170R/170G/170B filter the incident light to thereby obtainred, green and blue lights, respectively. For illustration, the colorfilters 170R/170G/170B include a dyed or pigmented material such aspolymer, or other suitable material.

The micro-lenses 180 are formed on the color filters 170R/170G/170B andin the pixel regions 100R/100G/100B respectively. The micro-lenses 180focus the incident light onto the photo sensitive elements120R/120G/120B. For illustration, the micro-lenses 180 are formed of anymaterial that may be patterned and formed into lenses with hightransmittance, such as acrylic polymer and other suitable material.

Referring to FIGS. 2A-2B, FIGS. 2A-2B illustrate enlarged partial viewsof the image sensor device 100 shown in FIG. 1 in accordance withvarious embodiments. Each of the convex dielectric lenses 140 has awidth W and a height H. As shown in FIG. 2A, the width W of the convexdielectric lens 140 is substantially identical to a distance D betweentwo opposite sides of the grid 150, and the height H of the convexdielectric lens 140 is substantially identical to a thickness T of thesecond dielectric layer 134. Alternatively, the height H of the convexdielectric lens 140 may be smaller than the thickness T of the seconddielectric layer 134. In such cases, the convex dielectric lens 140 isentirely in the second dielectric layer 134. In some embodiments, asshown in FIG. 2B, the height H of the convex dielectric lens 140 isgreater than the thickness T, such that a portion 142 of the convexdielectric lens 140 is in the second dielectric layer 134. The height Hof the convex dielectric lens 140 may vary in accordance with therefractive indexes of the convex dielectric lens 140, the firstdielectric layer 132 and the second dielectric structure 160. Further,in certain embodiments, the width W of the convex dielectric lens 140may be greater than the distance D.

Referring to FIGS. 3A-3H, FIGS. 3A-3H illustrate cross-sectionaldiagrams for fabricating an image sensor device 300 in accordance withsome embodiments of the present disclosure. In FIG. 3A, a substrate 310,photo sensitive elements 320R/320G/320B and pixel circuits322R/322G/322B are provided. The substrate 310 is a semiconductorsubstrate, which includes, but not limited to, a semiconductor wafer, asilicon-on-insulator (SOI) substrate or an epitaxial substrate. In someembodiments, the substrate 310 further includes an elementarysemiconductor, a compound semiconductor or an alloy semiconductor. Thephoto sensitive elements 320R/320G/320B are formed on the front side310A of the substrate 310 and in the pixel regions 300R/300G/300Brespectively. In some embodiments, the photo sensitive elements320R/320G/320B are formed by a diffusion process or an ion implantationprocess. For illustration, if the photo sensitive elements320R/320G/320B are PNP-type photodiodes formed by the ion implantationprocess, the photo sensitive elements 320R/320G/320B includes P-typepinned layers formed on N-type doped regions, and the substrate 310 is aP-type semiconductor substrate, in which the N-type doped regions areformed on the substrate 310. In addition, the pixel circuits322R/322G/322B are formed on the front side 310A of the substrate 310and adjacent the photo sensitive elements 320R/320G/320B respectively.

In FIG. 3B, a first dielectric layer 332 is formed on the back side 310Bof the substrate 310 opposite to the front site 310A. For illustration,the first dielectric layer 332 is formed by a deposition process such aschemical vapor deposition (CVD), physical vapor deposition (PVD), atomiclayer deposition (ALD), combinations thereof, or the like.

In FIG. 3C, a second dielectric layer 334 is formed on the firstdielectric layer 332. For illustration, the second dielectric layer 334is formed by a deposition process such as CVD, PVD, ALD, combinationsthereof, or the like. The first dielectric layer 332 and the seconddielectric layer 334 forms a first dielectric structure 330. In someembodiments, the material of the first dielectric layer 332 and thesecond dielectric layer 334 are selected, such that the first dielectriclayer 332 has a refractive index greater than the second dielectriclayer 334.

In FIG. 3D, an isolating layer 340 is formed on the second dielectriclayer 334. In some embodiments, the isolating layer 340 includes aninsulating material such as silicon oxide, silicon nitride, siliconoxynitride, combinations thereof, or the like. In some embodiments, theisolating layer 340 includes a metal material such as aluminum, copper,or the like, a metal alloy material such as aluminum alloy, copperalloy, or the like, a metal nitride such as titanium nitride, tantalumnitride, or other suitable material. For illustration, the isolatinglayer 340 is formed by a deposition process such as CVD, PVD, or anysuitable process.

In FIG. 3E, a grid 342 and recesses 344R/344G/344B are formed by anetching process. The recesses 344R/344G/344B are formed by removingparts of the isolating layer 340 and the second dielectric layer 334.For illustration, the etching process includes dry etching, wet etching,drilling, combinations thereof, or the like. Bottoms of the recesses344R/344G/344G directly adjoin the first dielectric layer 332. The grid342 is also formed for separating the pixel regions 300R/300G/300B afterthe etching process is done.

In FIG. 3F, convex dielectric lenses 350 are formed in the recesses344R/344G/344B and directly on the first dielectric layer 332. Theconvex dielectric lenses 350 are formed by a deposition process such asCVD, PVD, or the like. In each of the pixel regions 300R/300G/300B, theconvex dielectric lens 350 is formed to have a convex side 350A orientedopposite to one of the photo sensitive elements 320R/320G/320B and aplanar side 350B oriented toward one of the photo sensitive elements320R/320G/320B. The material of the convex dielectric lenses 350 isselected to have a refractive index smaller than that of the firstdielectric layer 332. In some embodiments, the refractive index of eachof the convex dielectric lenses 350 is smaller than the seconddielectric layer 334.

In the pixel regions 300R/300G/300B, the width and height of the convexdielectric lenses 350, the thickness of the second dielectric layer 334and the width of the recesses 344R/344G/344G (i.e. the distance betweentwo opposite sides of the grid 342) are adjustable in accordance withvarious embodiments. In some embodiments, the width of each of theconvex dielectric lenses 350 is substantially equal to or greater thanthe width of each of the recesses 344R/344G/344G. In some embodiments,the height of each of the convex dielectric lenses 350 is substantiallyequal to or greater than the thickness of the second dielectric layer334.

In FIG. 3G, a second dielectric structure 360 is formed on the firstdielectric structure 330, the convex dielectric lenses 350 and the grid342. The second dielectric structure 360 is formed to fill in therecesses 344R/344G/344B. For illustration, the second dielectricstructure 360 is formed by a deposition process such as CVD, PVD, ALD,combinations thereof, or the like. The material of the second dielectricstructure 360 is selected to have a refractive index smaller than thatof each of the convex dielectric lenses 350. In some embodiments, thesecond dielectric structure 360 at least partially covers the convexdielectric lenses 350.

In FIG. 3H, color filters 370R/370G/370B are formed on the seconddielectric structure 360. For illustration, the color filters370R/370G/370B are selectively patterned and sequentially formed by anexposure and development process using a photo-mask.

Further, in FIG. 3H, micro-lenses 380 are respectively formed on thecolor filters 370R/370G/370B. For illustration, the micro-lenses 380 areformed using a material in a liquid state by a spin-on technique. Suchmethod is performed to produce a substantially planar surface andmicro-lenses 380 with a substantially uniform thickness. In someembodiments, other methods, such as CVD, PVD, and/or the like, are alsoperformed for forming the micro-lenses 380.

Referring to FIG. 4 with FIGS. 3A-3H, FIG. 4 is a flow chart of a method400 for fabricating an image sensor device in accordance with someembodiments. The method 400 begins at operation 402, where a substrate310 is provided, as shown in FIG. 3A. At operation 404, a photosensitive element 320R/320G/320B is formed on a front side 310A of thesubstrate 310 for receiving incident light transmitted through thesubstrate 310. At operation 406, a pixel circuit 322R/322G/322B isformed on the front side 310A of the substrate 310 for electricalinterconnection with the photo sensitive element 320R/320G/320B. Atoperation 408, a first dielectric structure 330 is formed on the backside 310B of the substrate 310. In some embodiments, the firstdielectric structure 330 includes a first dielectric layer 332 formed onthe back side 310B and a second dielectric layer 334 formed on the firstdielectric layer 332, as shown in FIGS. 3B-3C. At operation 410, aninsulating layer 340 is formed on the first dielectric structure 330, asshown in FIG. 3D. At operation 412, a grid 342 and a recess344R/344G/344B are formed by performing an etching process to removeparts of the isolating layer 340 and a portion of the first dielectricstructure 330, as shown in FIG. 3E. At operation 414, a convexdielectric lens 350 is formed in the recess 344R/344G/344B, as shown inFIG. 3F. At operation 416, a second dielectric structure 360 is formedon the first dielectric structure 330, the convex dielectric lens 350and the grid 344, as shown in FIG. 3G. At operation 418, a color filter370R/370G/370B is formed on the second dielectric structure 360, and amicro-lens 380 is formed on the color filter 370R/370G/370B, as shown inFIG. 3H.

In accordance with the embodiments of the present disclosure, anadditional convex dielectric lens is formed between a color filter and asubstrate in each pixel region of an image sensor device, and the convexdielectric lens has a refractive index greater than that of a dielectricstructure on a convex side of the convex dielectric lens. Thus, incidentlight is condensed into a photo sensitive element in a more effectivemanner, such that the quantum efficiency of the image sensor device isimproved. In addition, since the crosstalk issue is avoided, the SNR ofthe image sensor device increases.

It is noted that, the aforementioned convex dielectric lenses in thepresent disclosure may be replaced with concave dielectric lenses inaccordance with various embodiments. For example, a concave dielectriclens may be formed in replace of the aforementioned convex dielectriclens in each pixel region to have a planar side oriented toward incidentlight and a concave side oriented toward the photo sensitive element,and the concave dielectric lens has a refractive index greater than thatof the aforementioned second dielectric structure and smaller than thatof the aforementioned first dielectric layer. Further, in someembodiments, the first dielectric structure is a single layer structure,and the convex dielectric lenses directly adjoin the back side of thesubstrate.

In accordance with some embodiments, an image sensor device includes asemiconductor device, a plurality of photo sensitive regions, adielectric layer, a grid structure, and a plurality of convex dielectriclenses. The plurality of photo sensitive regions are in thesemiconductor substrate. The dielectric layer is on a backside surfaceof the semiconductor substrate facing away from the plurality of photosensitive regions. The grid structure is on a backside surface of thedielectric layer facing away from the semiconductor substrate. The gridstructure includes a plurality of grid lines spaced from each other. Theplurality of convex dielectric lenses are alternately arranged with theplurality of grid lines of the grid structure on the backside surface ofthe dielectric layer. Apexes of the plurality of convex dielectriclenses are lower than top ends of the plurality of grid lines of thegrid structure.

In accordance with some embodiments, an image sensor device includes asemiconductor substrate, a plurality of photo sensitive regions, a firstdielectric layer, a plurality of convex dielectric lenses, a dielectricstructure, a layer of color filters, and a plurality of micro-lenses.The plurality of photo sensitive regions are in the semiconductorsubstrate. The first dielectric layer is on a backside surface of thesemiconductor substrate facing away from the plurality of photosensitive regions. The plurality of convex dielectric lenses are on abackside surface of the first dielectric layer facing away from thesemiconductor substrate. The dielectric structure is over convex sidesof the plurality of convex dielectric lenses. The layer of color filtersis on a backside surface of the dielectric structure facing away fromthe plurality of convex dielectric lenses. The plurality of micro-lensesare on a backside surface of the layer of color filters facing away fromthe dielectric structure. The plurality of micro-lenses respectivelyoverlap the plurality of convex dielectric lenses, and each of theplurality of micro-lenses laterally extends past opposite edges of acorresponding one of the plurality of convex dielectric lenses.

In accordance with some embodiments, an image sensor device includes asemiconductor substrate, a plurality of photo sensitive regions, a layerof a first dielectric material, a plurality of convex dielectric lenses,a lower grid structure, and an upper grid structure. The plurality ofphoto sensitive regions are in the semiconductor substrate. The layer offirst dielectric material is on a backside surface of the semiconductorsubstrate farthest from the plurality of photo sensitive regions. Theplurality of convex dielectric lenses are on a backside surface of thelayer of the first dielectric material farthest from the semiconductorsubstrate. The lower grid structure is on the backside surface of thelayer of the first dielectric material. The lower grid structureincludes a plurality of lower grid lines alternately arranged with theplurality of convex dielectric lenses from a cross-sectional view. Theplurality of lower grid lines are formed of a second dielectric materialhaving a lower refractive index than the first dielectric material. Theupper grid structure has a plurality of upper grid lines respectivelyover the plurality of lower grid lines of the lower grid structure fromthe cross-sectional view.

Although the present embodiments and their advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. An image sensor device, comprising: asemiconductor substrate; a plurality of photo sensitive regions in thesemiconductor substrate; a dielectric layer over a backside surface ofthe semiconductor substrate facing away from the plurality of photosensitive regions; a grid structure over a backside surface of thedielectric layer facing away from the semiconductor substrate, the gridstructure comprising a plurality of grid lines, wherein each of theplurality of grid lines comprises a lower portion and an upper portionforming an interface with the lower portion; and a plurality of convexdielectric lenses alternately arranged with the plurality of grid linesof the grid structure over the backside surface of the dielectric layer,wherein apexes of the plurality of convex dielectric lenses are higherthan an interface between the upper portion and the lower portion ofeach of the plurality of grid lines.
 2. The image sensor device of claim1, wherein the lower portion of each of the plurality of grid lines hasa refractive index greater than a refractive index of each of theplurality of convex dielectric lenses.
 3. The image sensor device ofclaim 1, wherein the lower portion of each of the plurality of gridlines has a refractive index less than a refractive index of thedielectric layer.
 4. The image sensor device of claim 1, wherein thedielectric layer has a refractive index greater than a refractive indexof each of the plurality of convex dielectric lenses.
 5. The imagesensor device of claim 1, wherein the upper portion of each of theplurality of grid lines has a height greater than a height of the lowerportion of each of the plurality of grid lines.
 6. The image sensordevice of claim 1, wherein the lower portion of each of the plurality ofgrid lines has a height less than a height of each of the convexdielectric lenses.
 7. The image sensor device of claim 1, wherein eachof the plurality of convex dielectric lenses has opposite edgesrespectively in contact with two of the plurality of grid lines.
 8. Theimage sensor device of claim 1, further comprising: a dielectricstructure interfacing the apexes of the plurality of convex dielectriclenses.
 9. The image sensor device of claim 8, wherein the dielectricstructure has a refractive index less than a refractive index of each ofthe plurality of convex dielectric lenses.
 10. An image sensor device,comprising: a semiconductor substrate; a plurality of photo sensitiveregions in the semiconductor substrate; a first dielectric layer over abackside surface of the semiconductor substrate facing away from theplurality of photo sensitive regions; a plurality of convex dielectriclenses over a backside surface of the first dielectric layer facing awayfrom the semiconductor substrate; and a second dielectric layer over thebackside surface of the first dielectric layer, the second dielectriclayer having a plurality of portions alternately arranged with pluralityof convex dielectric lenses, wherein a top position of one of theplurality of portions of the second dielectric layer is lower than a topposition of one of the plurality convex dielectric lenses.
 11. The imagesensor device of claim 10, further comprising: a grid over the seconddielectric layer, wherein the grid has a plurality of grid linesrespectively aligned with the plurality portions of the seconddielectric layer.
 12. The image sensor device of claim 11, wherein thegrid includes a metal material.
 13. The image sensor device of claim 11,wherein the grid includes a dielectric material.
 14. The image sensordevice of claim 10, wherein the first dielectric layer has a refractiveindex greater than a refractive index of the second dielectric layer.15. The image sensor device of claim 14, wherein the refractive index ofthe first dielectric layer is greater than a refractive index of one ofthe plurality of convex dielectric lenses.
 16. An image sensor device,comprising: a semiconductor substrate; a plurality of photo sensitiveregions in the semiconductor substrate; a layer of a first dielectricmaterial over the semiconductor substrate; a plurality of convexdielectric lenses over the layer of the first dielectric material; alower grid structure over the layer of the first dielectric material,the lower grid structure having a height smaller than a height of theplurality of convex dielectric lenses; and an upper grid structure overthe lower grid structure and formed of a material different than amaterial of the lower grid structure, wherein the upper grid structurehas a height larger than the height of the lower grid structure.
 17. Theimage sensor device of claim 16, wherein a topmost position of one ofthe plurality of convex dielectric lenses is higher than an interfacebetween the lower grid structure and the upper grid structure.
 18. Theimage sensor device of claim 16, further comprising: a dielectricstructure interfacing the plurality of convex dielectric lenses, thelower grid structure, and the upper grid structure.
 19. The image sensordevice of claim 18, wherein the dielectric structure has a refractiveindex less than a refractive index of one of the plurality of convexdielectric lenses.
 20. The image sensor device of claim 18, furthercomprising: a plurality of color filters over the dielectric structure;and a plurality of micro-lenses over the plurality of color filters,respectively.